Added Inkwell lightpen drivers for the C64 and the C128.

They use the mouse driver programming interface.

Added a test program for lightpen drivers.  Now, it knows about only those two drivers; it will need updating when others are added.

asminc/c64.inc

@@ -95,6 +95,9 @@ VIC_CTRL2       := $D016
 
 VIC_HLINE       := $D012
 
+VIC_LPEN_X      := $D013
+VIC_LPEN_Y      := $D014
+
 VIC_VIDEO_ADR   := $D018
 
 VIC_IRR         := $D019        ; Interrupt request register
@@ -207,4 +210,3 @@ TP_FAST         = $80           ; Switch Rossmoeller TurboProcess to fast mode
 
 RAMONLY         = $F8           ; (~(LORAM | HIRAM | IOEN)) & $FF
 
-